kegentile

This plugin will create a tag cloud for a specific author. This will allow a visitor on your site to drill deep down into an author’s specific content.
It uses all of the same parameters as wp_tag_cloud(), but adds an additional one for the author_id. When the author_id is passed an integer of a published author that has tagged his or her posts, a tag cloud will be generated.
It will also create a new permalink structure on your site of
www.yoursite.com/author/author-slug/tag/tag-slug
***Note: that you must be using any custom permalink structure for this plugin to function. Also, custom taxonomies is currently not functioning with this version, please look forward for this in a later version.

Author Tag Cloud

Creates a template tag to create an author specific tag cloud and creates a new permalink structure to drill down into content by author and tag.

D'Arcy Norman

The plugin gives users the oportunity to embed a tag cloud for a site within any page. 
When using the shortcode [tagcloud] when 
writing in the content of any page, the user includes in the page, a 
tag cloud for posts on that site.
I am working on adding the ability to set options, such as sizes, etc…

Author Tag Cloud vs Tag Cloud Shortcode